What could be the cause of a light pink-brown color after adding the UniVer® 3 reagent?

Document ID

Document ID TE293

Version

Version 2.0

Status

Status Published

Published Date

Published Date 27/05/2017
Question
What could be the cause of a light pink-brown color after adding the UniVer® 3 reagent?
Summary
Light pink-brown color forms after adding the UniVer® 3 reagent
Answer
If there is hardness in the sample, the color after adding UniVer® 3 should be pink or red. Iron and manganese can interfere with the UniVer3 and cause the pink-brown color, and also interfere with the endpoint color.

Repeat the test with a fresh sample, but add 1-2 drops of the Hardness 3 titrant first, then add the UniVer® 3, and then continue adding the drops of the Hardness 3 solution. The titrant complexes with the iron and manganese so that they will not interfere with the reagent. Include the initial drops when determining the hardness concentration.